Aluminum – Zinc alloy

Types of Alloys:

• Zinc-aluminum alloy containing 5% aluminum
• Zinc-aluminum alloy containing 7%-10% aluminum
• Zinc-aluminum alloy containing 15% aluminum
• Zinc-aluminum alloy containing 20% aluminum
• Zinc-aluminum alloy containing 30% aluminum

Application Scope:

• Galvanizing of large quantities of structural parts
• Galvanizing of steel pipes by blowing
• Galvanizing of high-speed materials
• Galvanizing of building materials
• Galvanizing of steel frames
• Galvanizing of high temperature bolts

Effect of Aluminum Plating Alloy:

• Increase the brightness of the coating
• Reduce the oxidation of the zinc liquid surface and zinc dust
• Function to thin the coating
• At 465°C, when the aluminum content is greater than 0.134%, the bottom slag in the zinc pot will be converted into powder slag.

Aluminum Content Control Standard in Liquid Zinc:

• Galvanizing of mass-produced structural parts; the aluminum content is controlled at 0.002% ~ 0.007%
• Galvanizing of steel pipes by blowing: the aluminum content is controlled at 0.05% ~ 0.13%
• Galvanizing of high-speed materials: the aluminum content is controlled at 0.002% ~ 0.02% (be careful when producing products with coating thickness requirements)
• Galvanizing of building materials: depends on product output
• Galvanizing of high temperature bolts: the aluminum content is controlled above 0.05%

Zinc-aluminum Alloy Addition Method:

• For mass galvanizing, add the alloy to the special shock cage rotor motor, use a tool to press into the zinc liquid surface to a depth of 30-50cm, and then slowly melt it along the length of the zinc pot.
• For galvanized pipes, it should be added according to the brightness of the pipe and the thickness of the zinc layer. When adding, it should be added evenly at different times and different positions.
• For high-speed materials, it should be added carefully according to the coating thickness requirements, and the alloy with different content should be selected from the mass galvanized.
• For building materials: the addition method is the same as mass galvanizing.
• For high temperature bolts: add at regular intervals.

Points for Attention:

• Each company should choose zinc-aluminum alloy with different aluminum content to use based on specific production conditions (i.e. different products, different requirements).
• The addition of alloy must be added in batches according to the production volume. Do not add the required amount of a shift at one time, and follow the principle of small amount and multiple times.
• The addition position is not accurate, adding too much at one time, the addition operation is not accurate, the concentration of the plating auxiliary agent is not correct, or the problems of the concentration ratio of zinc chloride and ammonium chloride,… will all cause plating leakage and increase the amount of zinc ash.
• Galvanizing pipe companies should choose alloys instead of aluminum ingots, aluminum billets with high melting point, not easy to melt, which greatly affects the life of the zinc pot. Products with coating thickness requirements must be used correctly.

Table 3. Melting Point with Different Nickel Element Content: